WARNING: GRAPHIC CONTENT Critics have long questioned the official conclusion that the impact of hijacked planes caused the Twin Towers to collapse
Conspiracy theorists claim grainy footage apparently taken during the 9/11 attacks proves bombs were planted in the World Trade Center .
A video uploaded on YouTube appears to show an explosion in the South Tower on the day of the atrocity, some theorists say.
They claim the blast occurred several floors below the point where a plane was smashed into the building by hijackers.
The force of the explosion propels what looks like a body out of the window.
Al-Qaeda terrorists crashed the Boeing 767-200 plane into the famous skyscraper minutes after another aircraft had been flown into the North Tower on September 11, 2001.
A total of 2,996 people were killed in the co-ordinated attacks 16 years ago.
Official investigations have found that the buildings – which each had 110 storeys – collapsed because of the impact from the planes.
But conspiracy theorists have long disputed this, and the video has been cited as “proof” that explosives were also used during the atrocity.
Posting below the video, Mike Wayne wrote: “This really s***s on the “dust puffs and air pressure” claim of the official lie.”
The official explanation is that puffs of smoke from the towers was air pressure caused by collapsing floors, the Daily Star reports.
But John-Michael Talboo, from Architects & Engineers for 9/11 Truth, said of videos of the attacks: “There is no reason, on the ‘dust puff’ theory, for such blasts to be as isolated as they were.”
The day after the attack, US President Donald Trump gave a TV interview which appeared to suggest the World Trade Center buildings collapsed because of bombs.
He said: “It wasn’t architectural defect. How could a plane, even a 767 or 747 or whatever it might have been; how could it possibly go through that steel?
“I happen to think that they had not only a plane, but they had bombs – bombs that exploded simultaneously.
“Because I can’t imagine anything being able to go through that wall.”
Experts have cast doubt on whether the seeming explosions were caused by bombs, however.
An investigation by the Federal Emergency Management Agency (FEMA) concluded that the impact of the planes caused the buildings to collapse.
Structural engineers who worked on the FEMA investigation believe that the puffs of smoke were caused by a process known as ‘pancaking’.
This is what happens when floors collapse downward in a chain reaction, rather than a bomb being detonated.
The 9/11 atrocity was the worst single act of terrorism in history. Al-Qaeda carried out co-ordinated attacks on the Twin Towers and the Pentagon 16 years ago.